Density profile reconstruction using HIBP in ECRH plasmas in the TJ-II stellarator

Abstract

Heavy Ion Beam Probing (HIBP) is a unique tool for plasma potential measurements. In the TJ-II stellarator (CIEMAT, Madrid, Spain) HIBP is capable to move the sample volume (SV) from Low Field Side (LFS) of a plasma column through the plasma center to High Field Side (HFS), so the time evolution of plasma potential φ and secondary beam total current Itot radial profiles can be obtained during one shot. Itot is proportional to the plasma density ne at the SV, it is affected by attenuation factors along the beam trajectory. The work shows the method for the ne radial profile reconstruction from HIBP Itot signal. Using the method, for the first time ne radial profiles are reconstructed from HIBP Itot signal in TJ-II regimes with electron cyclotron resonance heating (ECRH) and the line-averaged electron density n̄e up to 0.8 · 1019 m−3. Reconstructed ne(ρ) profiles are consistent with Thomson scattering data.